A safety and arming device is a required element of a munition to ensure that the munition is not armed and detonated until the desired time. The safety and arming device (S & A) is part of a munition's fuze and prevents arming of the fuze until certain conditions are met.
Many safety and arming devices require two environments or occurrences for operation and initiation of the fuze. The environments are two independent physical events which must be sensed by the projectile or munition prior to allowing arming. The first environment utilized is usually setback, which is both easily sensed and well known in the art. For example, commonly assigned patent U.S. Pat. No. 5,693,906 describes a first environment sensing device which utilizes setback. The second environment can be based on a number of different parameters such as timing, barrel escape, turns counting, etc. In addition, various techniques for determining muzzle or bore exit are known. For example, commonly assigned patents U.S. Pat. No. 5,497,704 and U.S. Pat. No. 5,265,539 both utilize magnetic sensors to determine muzzle exit. Commonly assigned patent U.S. Pat. No. 5,275,107 determines muzzle exit based on setback acceleration going to zero. The entire contents of commonly owned patents U.S. Pat. Nos. 5,693,906, 5,497,704, 5,265,539 and 5,275,107 are hereby incorporated by reference.
All of these prior art techniques for determining the second environment of muzzle exit require additional circuitry, which adds to the complexity of the device. What is needed is a technique for determining the second environment of muzzle exit with the circuitry which is already included in the munition.